New Joints Less Successful in RA Patients

Action Points

Explain that a meta-analysis of 40 studies found an increased risk of hip dislocation and knee infection for patients with rheumatoid arthritis versus osteoarthritis who underwent total hip or knee replacement.

Note that far more patients with OA than RA were included in these studies and that other outcomes such as revision surgery, 90-day mortality, or 90-day thromboembolism were not different depending on the underlying type of arthritis.

Patients with rheumatoid arthritis (RA) who undergo hip or knee replacement surgery are at greater risk for certain complications such as hip dislocation and knee infection than osteoarthritis (OA) patients, a meta-analysis found.

In studies that assessed the rate of hip dislocation in RA patients within 5 years of arthroplasty, there was "strong evidence" for increased risk compared with OA patients, with an adjusted odds ratio for this outcome of 2.16 (95% CI 1.52 to 3.07), according to Bheeshma Ravi, MD, and colleagues from the University of Toronto.

In addition, in a study that adjusted for age, sex, and surgical factors, the hazard ratio for infection among RA patients undergoing total knee replacement was 1.86 (95% CI 1.31 to 2.63), the researchers reported in the December Arthritis & Rheumatism.

Far more joint arthroplasty procedures are done for patients with OA, and the few studies that have compared outcomes in RA and OA patients have had conflicting results.

"As RA is fundamentally different from OA in terms of pathogenesis, prognosis, and medical management, systematic differences in [total joint arthroplasty] outcomes would be expected," Ravi and colleagues wrote.

This uncertainty about outcomes for RA patients interferes with the ability of patients and clinicians to make informed decisions about joint replacement.

To address this need, the researchers undertook a systematic review and meta-analysis in which they identified 40 studies that considered potential complications of these procedures.

Outcomes of interest were revision, infection, dislocation, 3-month mortality, and the 90-day occurrence of venous thromboembolism. There proved to be significant differences only in hip dislocation and knee infection.

In four studies that assessed the likelihood of revision after hip arthroplasty within 5 years, the unadjusted odds ratio for RA patients was 1.33 (95% CI 1.03 to 1.71), but in a study that adjusted for age, sex, and comorbid conditions, no increased risk was seen during the first year (OR 1.11, 95% CI 0.82 to 1.51).

There also were no differences in need for hip revision between years 6 and 10, and the risk of hip revision beyond year 10 actually was lower for RA patients (OR 0.28, 95% CI 0.17 to 0.47).

For knee revision, a meta-analysis of three studies found a slight elevation in risk within the first 5 years (OR 1.24, 95% CI 1.10 to 1.40) for RA patients, but no differences were seen after that time point.

No increased risk for patients with RA was seen for mortality (OR 1.40, 95% CI 0.82 to 2.39) or venous embolism (OR 0.84, 95% CI 0.28 to 2.54) within 3 months of the surgery.

The most notable finding of this analysis -- that the risk of dislocation is elevated following hip replacement in RA patients -- was unexpected, the researchers observed.

"Susceptibility to dislocation could be the result of poorer soft tissue quality in RA relative to OA, resulting in suboptimal hip abductor strength postoperatively," Ravi and colleagues suggested.

Further research should explore this finding more fully, to identify surgical factors that might be modified to minimize the likelihood of post-surgical dislocations, they advised.

The increased risk in dislocations was not accompanied by a greater need for revision in patients with RA.

A possible explanation for this, according to the authors of the meta-analysis, could be that such dislocations may be more commonly managed nonsurgically, such as through modification of physical activity.

The greater risk for infection in RA patients "makes intuitive sense," they noted, because of the wide array of powerful immunosuppressives currently used in the management of RA.

There were several limitations to this analysis, the authors conceded.

Some cases of RA may have been misclassified, not all studies controlled for important factors such as age and comorbidities, and patient-level data were unavailable.

There also was some heterogeneity across the studies, but in most cases the I2 values were 50% or less, suggesting moderate heterogeneity at most.

Additional well-powered studies should be done to confirm these findings and to investigate other potentially meaningful factors, such as the influence of biologic treatments and underlying bone health.

"The results of such studies would be useful to guide decision-making regarding [total joint arthroplasty] in the setting of RA," Ravi and colleagues concluded.

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